Cryogenic vaporizer



Dec. 27, 1966 L. TYREE, JR 3,293,871

CRYOGENIC VAPORIZER Filed May 13, 1965 2 Sheets-Sheet 2 i I i a I MM TM United States Patent 3,293,871 CRYOGENIC VAPORIZER Lewis Tyree, Jr., Chicago, Ill., assignor to General Dynamics Corporation, New York, N.Y., a corporation of Delaware Filed May 13, 1965, Ser. No. 455,448 6 Claims. (Cl. 62-52) The present invention relates generally to cryogenic Vaporizers, and more particularly is directed to a cryogenic vaporizer having improved heat transfer characteristics.

It is highly advantageous to transport and store many gases, such as oxygen, nitrogen, argon, etc., in a liquid state due to the substantial reduction in size of the containers, which may be achieved. For example, ordinarily approximately 140 pounds of steel is required to contain each pound of a gas, such as hydrogen, being stored at high pressure. If such a gas is subjected to extremely low temperatures and liquefied, a substantial advantage is realized in that only about 11 pounds of steel is required for confining, the same amount of material.

However, effective use of this liquid storage concept requires the development of suitable cryogenic Vaporizers since the cold liquid is ordinarily required by the consumer in the form of a gas. Such apparatus includes a suitable heat source for warming the liquid. Atmospheric air has not normally been employed as a heat source, although its cost is substantially lower than other fuels, due to the relatively high costs of the associated heat transfer equipment. In addition, the heat transfer fins or vanes usually provided on cryogenic Vaporizers for effecting the heat transfer were usually quite expensive and far from satisfactory in operation. Ordinarily extruded aluminum vanes, having a generally wedgeshaped configuration, were provided about the circumference of the pipes. The particular configuration of the vanes was necessary because the thermal conductivity of aluminum decreased with a decrease in temperature, leading to thermal pinch unless the portions of the vane closest to the cold pipe were thicker so as to negate the effects of this phenomenon by providing more material available for transferring heat at the colder regions. Not only was such an extruded configuration expensive and inconvenient in installation, it was also highly ineffective in operation. It remained quite difficult to prevent icing on the vanes and even more ditficult to remove the ice after it had formed, particularly if attempts were made to employ atmospheric air as the heat source, since the water content in the air was deposited as ice. In many instances it was necessary to entirely stop the flow of the cold liquefied gas in order to permit the ice to be removed so that adequate heat transfer might be provided. Obviously this led to extreme inefl'iciencies in operation.

It is a principal object of the present invention to provide a vaporizer for cryogenic material which is provided with improved heat transfer characteristics.

It is another object of the present invention to provide a cryogenic vaporizer having improved heat transfer means which substantially preclude the formation of bridge type icing.

It is another object of the present invention to provide a cryogenic vaporizer having improved heat transfer characteristics so as to facilitate ice removal and maintain an efficient level of heat transfer.

It is still another object of the present invention to provide a cryogenic vaporizer having substantially improved heat transfer characteristics such that air at ambient temperatures may be employed for effecting heat transfer.

It is a further object of the present invention to provide a cryogenic vaporizer having an improved and simplified heat transfer means, which is relatively inexpensive "Ice and simple to fabricate, convenient to install, durable in use, and extremely efficient in operation.

Other objects and advantages will become readily apparent from the following detailed description and accompanying drawings wherein: Y

FIGURE 1 is a vertical sectional view of an apparatu in accordance with the present invention;

FIGURE 2 is a sectional view taken along line 22 of FIGURE 1;

FIGURE 3 is a sectional view taken along line 3. of FIGURE 1; and

FIGURE 4 is a fragmentary perspective view of a portion of the tubing and itsassoci-ated heat transfer means fabricated in accordance with the present invention.

Referring to the drawings, an apparatus in accordance with the present invention generally includes a fluid inlet 10 which is supplied with the extremely cold liquefied gas from an external source (not shown), a fluid outlet 12 serially coupled to the inlet 10 and adapted for supplying the fluid which has undergone a transition and returned to its gaseous state to a desired gas receiving means (not shown), and a heat transfer means 14 which communicates with a source of ambient temperature heating 16. i

More particularly, an apparatus in accordance with the principles of the present invention is generally illustrated in a vertically upright position. The apparatus is normally operated in a vertical. position so ,as to aid in minimizing water deposition and ice buildup. Generally, the inlet 10 and outlet 12 are serially coupled by the provision of a plurality of similar, parallel spaced, vertically extending tubes which are preferably arranged in a generally circular configuration.

In the disclosed embodiment the individual tubes are interconnected in series relationship. However, it is also possible to arrange these tubes in parallel relationship between the fluid inlet and the fluid outlet.

The circular arrangement is advantageous in that it facilitates efficiently supplying ambient temperature air to the heat transfer means as well as facilitating the fabrication of a composite, integral structure.

The fluid'inlet 10 is generally coupled to the source of fluid through a suitable pipe union 18, which may be provided with a support bracket for carrying a portion of the weight of the apparatus. The inlet 10 is coupled to a. tube 20, which extends vertically upwardly a predetermined distance and is coupled to one end of a horizontally extending pipe nipple 22, preferably by a suitable pressure-tight coupling. In this connection, the upper end of the tube 20 is preferably connected to the pipe nipple 22 in generally pressure-tight relationship by a suitable swagelock 24. Such a pressure-tight coupling is generally desirable in view of the relatively high pressures anticipated. The opposite end of the pipe nipple 22 is connected to a vertically downwardly extending tube 26, similar to the tube 20, by a similar sw agelock 28. In this manner fluid communication is provided between the fluid inlet 10 and the tube 26.

' The tube 26 extends vertically downwardly a predetermined distance generally parallel to the tube 2 0 and is of approximately the same axial length. The end of the tube 26 opposite to that connected to the pipe nipple 22 is coupled to a pipe nipple 30, which is generally similar to the pipe nipple 22, by a swagelock 32 generally similar to the previously mentioned swagelocks. The opposite end of the pipe nipple 30 is coupled through another similar swagelock 34 to one end of another similar tube 36 which extends vertically upwardly, terminating adjacent the upper end of the tube 26, and is coupled to another similar pipe nipple 38 through another similar sw'agelock 40. The pipe nipple 38 is then coupled to another simwardly extending tube 44.

ilar swagel'ock 42 which is coupled to a vertically down- In this manner a desired number of parallel vertically extending tubes are serially coupled to the fluid inlet 10. A final vertical tube 46 is coupled through a swagelock 48, similar to those previous-1y described, to the outlet 12. It has been found advantageous to employ approximately tubes in fabricating the apparatus. Preferably the tubes are arranged so as to define the circumference of a circle, as previously mentioned. This circular arrangement permits efiicient supply of the ambient temperature air to the heat transfer means. Since the fluid inlet 10 and the fluid outlet 12 are serially connected, substantially all of the cold fluid is subjected to approximately the same amount of heat transfer processing as it flows through the apparatus.

The outlet 12 is provided with a union 50 similar to the union 18 such that it may be readily coupled to a desired apparatus which is to receive the gas.

Although the fluid inlet 10 and the fluid outlet 12 are serially coupled, the above-described construction in effect provides a plurality. of separate longitudinally extending tubes arranged such that each tube may be conveniently provided with suitable heat transfer means and a composite integral structure formed.

It is generally advantageous to provide all of the tubes with similar, suitable heat transfer means. Since all of the tubes are approximately the same length, this provision may be conveniently made, and in addition the associated heat transfer fins provided on adjacent tubes may be readily interconnected to provide an integral, selfsupporting structure.

A tube 52 provided with a heat transfer fin 54 in accordance with the principles of the present invention is illustrated in FIGURE 4. The heat transfer fin 54 comprises an elongated, relatively thin sheet of a preselected thermally conductive material secured to the tube 52. The sheet is preferably of substantially uniform thickness and is generally somewhat longitudinally shorter than the tube 52 so that the opposed ends of the tube 52 may be conveniently serially connected to adjacent tubes by suitable swagelocks and pipe nipples. The sheet is suitably shaped to form a plurality of longitudinally extending fins 58, 59, 60 and 61 connected to the tube 52. The fins 58, 59, 60 and '61 are inthermal contact with the tube 52, and extend outwardly from its circumference. The sheet is formed to include a web 62 which is spaced from the tube 52 and interconnects the outer edges of the fins 58 and '59. This results in the provision of a longitudinally extending surface, parallel to and spaced. from the cold tube 52 and in thermal communication with the tube 52. Such a provision is highly advantageous in that it permits the web 62 to serve as a defroster panel, as is subsequently explained.

The portion of the sheet defining the fins 58 and 59 and the web 62 forms a member, which is generally triangular in section, with the tube 52 serving as the vertex. Preferably, the triangle defined is generally isosceles with the fins 58 and 59 serving as the equal legs so as to provide the same heat transfer surface area on opposed sides of the tube 52.

The fins 60 and 61 define the opposed ends of the sheet,

and extend outwardly from the tube 52 forming a generally obtuse angle with the fins 58 and 59 with which they are respectively integrally connected. The fins 60 and 61 thus extend outwardly from the tube 52 in a direction generally opposite to the fins 58 and 59 so as to provide efficient heat transfer around substantially the entire periphery of the tube 52. The fins are secured in thermal contact with the tube 52 by suitable means. Preferably, this is achieved by soldering the sheet to the tube 52 along the line defined by the vertices of the obtuse angles formed by the fins 58 and 61 and by the fins 59 and 60. Thus, the sheet is secured to the tube 52 by a structurally strong, thermally eflicient junction.

All of the tubes forming the circular configuration are provided with heat trans-fer fins which are substantially similar to the heat transfer fin 54. Preferably, the heat transfer fins are all secured to their associated tubes by soldering, as described above. In addition, the opposed ends of the webs on adjacent heat transfer fins are main tained in thermal contact. If desired these opposed ends may be interconnected and maintained in thermal contact by suitable means, such as soldering, so as to form a composite integral structure.

It is desirable to form the sheets comprising the heat transfer fins so that there is no interference between the fins on adjacent tubes corresponding to the fins 60 and 61. In this connection these fins are formed so as to extend unequal distances outwardly from their associated tubes. Thus, the fin 61 extends outwardly from the tube 52 a lesser distance than does the fin 60. Similarly, a tube 64 adjacent the tube 52 includes a heat transfer means 66 similar to the heat transfer means 54. The heat transfer means 66 includes a relatively short fin 68 adjacent the relatively long fin 60 on the tube 52 and a relatively long fin 70 extending in the direction of the next adjacent tube 72.

The tubes are fabricated of a structurally strong, highly durable, non-corrosive material, such as brass. The sheets of material comprising the heat transfer fins pro- Nided for the tubes are fabricated of a material having the property of a thermoconductivity which increases with a decrease in temperature. This selection of material is highly advantageous, as is subsequently explained. A preferred material is copper, which is readily available and is relatively inexpensive. Either relatively pure copper or electrolytic tough copper may be employed. Moreover, copper, in relatively thin sheets, is deformable and may be conveniently bent into a desired shape. Thus, is may be readily formed into the previously described shape.

In order to provide ambient temperature heating for the heat transfer means, a suitable fan or blower is provided and suitably arranged with respect to the heat transfer fins to direct a generally constant stream of air, preferably at ambient temperatures, across all of the heat transfer fins.

Generally, the fan 80 is disposed at a predetermined distance above the upper ends of the vertically extending tubes and their associated heat transfer fins. This is to provide a spacing for the swagelocks and nipples interconnecting the upper ends of adjacent tubes.

As previously mentioned, the adjacent tubes and their associated interconnected heat transfer fins form a generally circular configuration. The fan 80 is coupled to this composite structure such that the ambient temperature air may be efficiently supplied to the heat transfer fins. In this connection, a suitable ring 82 is secured about the upper end of the composite heat transfer means 14 which includes the individual adjacent interconnected heat transfer fins. An annular spacer 84 is secured intermediate to the ring 82 and the heat transfer means 14.

The fan 80 is of slightly larger diameter than the diameter of the ring 82 which is disposed about the outer periphery of the composite heat transfer means 14. Accordingly, the fan 80 is coupled to the heat transfer means 14 by the provision of a suitable annular transition reducer 86 which extends from the fan 80 to the heat transfer means 14. Preferably the transition reducer 86 is bolted into position on both the fan 80 and on the ring 82. Thus, the ambient temperature air produced by the fan is supplied directly to the heat transfer fins in an efficient manner.

To provide additional structural rigidity as 'well as support for the apparatus, a second ring 88 is disposed about the lower end of the heat transfer means and coupled to a plurality of downwardly extending legs 90, so as to provide a spacing for the air supplied to flow out through the bottom of the structure. The legs 90 are preferably secured to a rigid base 92 which supports the apparatus. Preferably an annular spacer 94 is disposed intermediate the ring 88 and the heat transfer means 14.

In operation extremely cold liquefied gas is supplied to the inlet and passes through the plurality of serially connected tubes until it reaches the outlet 12 from which it is to be supplied to a desired apparatus. As the liquid gas passes through the tubing, it is heated above its critical temperature so that it returns to its gaseous state. To maintain eificient heating, it is desirable to prevent icing on the tubes and on the heat transfer fins. This is accomplished by suppling a flow of ambient temperature air, produced by the fan 80, downwardly across-the heat transfer fins which are in thermal contact with their respective sections of gas carrying tubing. Heat is thereby transferred from the ambient temperature air and by external radiation through the heat transfer fins and to the liquefied gas, warming the latter as it flows through the tubes. 7

The portions of each of the heat transfer fins closest to its associated tube is obviously at the lowest temperature so that icing and reduced heat transfer is most likely to occur at these regions. But, as previously mentioned, the material comprising the heat transfer means is selected to have a thermal conductivity which increases with a decrease in temperature. Thus, the colder regions of the heat transfer fins conduct more of the heat supplied :by the air than do the warmer regions, thereby negating ice formation. Moreover, this results in a tendency to provide more heat to the coldest regions so as to increase the efficiency of heat transfer.

In most instances icing still may occur on portions of the heat transfer fins. But, as previously described in detail in conjunction with FIGURE 4, each of the individual heat transfer means is provided with a web, or defroster panel defining a generally fiat surface which is maintained in parallel spaced relationship with its associ ated section of tubing and in thermal communication therewith. Ice is likely to form on this web only after the fins coupling .it to the associated tube become iced over because the web is spaced from the cold tube. Thus, this configuration results in the provisions of a 'heat transfer surface which is highly unlikely to become iced over, thereby in effect providing an exposed defroster panel substantially always available for heat transfer operations. Moreover, if ice does form on this defroster panel, it is easily removable due to the exposed nature of the defroster panel. This tendency of the defroster panel to quickly deice also promotes deicing of other portions of the fins by initiating loosening of the ice-tofin bond. In addition, adjacent web portions are interconnected in forming the composite heat transfer means 14, so that a peripheral exposed surface, or defroster panel, is provided which generally does not tend to ice over, and may be readily deiced in instances where icing does occur. This provision coupled with the inverse thermal conductivity of the copper comprising the fins insures substantial availability of efiicient heat transfer with little danger of curtailment of operation due to the formation of icing.

Since the copper sheets, comprising the heat transfer means, are of uniform thickness they may be conveniently and inexpensively fabricated, such as by cold rolling, and readily bent into the desired form.

Thus, an improved cryogenic vaporizer has been provided which is relatively convenient and inexpensive to manufacture and which provides substantially improved heat transfer characteristics.

-It will be understood that various modifications and changes will be apparent to those skilled in the art from the foregoing description. Such modifications are deemed to be within the scope of the appended claims.

Various features of the present invention are set forth in the following claims.

I claim:

1. An improved cryogenic vaporizer including a vaporizer tube, an inlet, and an outlet, said tube, said inlet, and said outlet being interconnected, comprising a plurality of fins secured to said tube in thermal communication therewith, said fins being formed of a single sheet of preselected material of substantially uniform thickness and being disposed in spaced, parallel relationship to the axis of said tube.

2. An improved cryogenic vaporizer comprising a tube having an inlet and an outlet and a heat transfer means thermally coupled to said tube, said heat transfer means including a plurality of fins formed of a thermally conductive material of substantially uniform thickness and extending outwardly from the periphery of said tube, and a web defining a defroster panel having a flat surface which is spaced from and generally parallel to the axis of said tube and interconnects the outer edges of two of said fins, hereby forming an exposed defroster surface which is spaced fromand thermally coupled to said tube.

3. An improved cryogenic vaporizer comprising a plurality of spaced, generally parallel, longitudinally extending tubes, means for coupling said tubes with each other, a plurality of longitudinally extending fins connected to each of said tubes, the fins associated with each of said separate tubes being formed of a single sheet of thermally conductive material of substantially uniform thickness, said sheet being shaped to form said plurality of 'fins extending outwardly from said tube and including a web which is spaced from said tube and interconnects the outer edge of two of said fins, and means for interconnecting the webs provided on adjacent tubes so as to define a peripherally extending exposed surface and form an integral self-supporting structure.

4. An improved cryogenic vaporizer having an inlet and an outlet comprising a plurality of spaced, generally parallel, longitudinally extending tubes arranged in a generally circular configuration, means for coupling said tubes and said inlet and outlet with each other, a plurality of longitudinally extending fins connected to each of said tubes, the fins associated with each separate tube being formed of a single sheet of a thermally conductive material having a thermal conductivity which increases with a decrease in temperature, said sheet being of substantially uniform thickness and being suitably shaped to form said plurality of fins extending outwardly from said tube and including a web spaced from said tube which interconnects the outer edge of two of said fins, said fins other than said two fins of each of said sheets extending unequal distances outwardly from said tube so as to remain spaced from corresponding fins provided on adjacent tubes, means for structurally and thermally interconnecting webs on adjacent tubes so as to form an integral selfsupporting structure, and means for passing ambient temperature air through said structure so as to pass over said fins.

5. An improved cryogenic vaporizer having an inlet and an outlet comprising a plurality of spaced generally parallel longitudinally extending tubes coupled with each other, means for coupling said inlet and said outlet through said plurality of coupled tubes, a plurality of longitudinally extending fins connected to each of said tubes in thermal communication therewith, the fins associated with each separate tube being formed of a single sheet of a material having a thermal conductivity which increases with a decrease in temperature and, each of said sheets being of substantially uniform thickness and, shaped to form said plurality of fins extending outwardly from said tube and including a longitudinally extending defroster panel interconnecting the outer edge of two of said fins, thereby forming an exposed surface spaced from and in thermal communication with said tube, means for interconnecting defroster panels on adjacent tubes so as to form an integral self-supporting structure, whereby a peripherally extending deicing surface is defined, said surface being spaced from and in thermal communication with said tubes, and blower means for passing air through said structure so as to pass over said fins and said peripherally extending surface.

6. An improved cryogenic vaporizer having an inlet and outlet comprising a plurality of spaced generally parallel longitudinally extending tubes coupled with each other, means for coupling said inlet and said outlet through said plurality of coupled tubes, a plurality of longitudinally extending fins connected to each of said tubes in thermal communication therewith, a plurality of longitudinally extending defroster panels each interconnecting the outer edges of two of said fins of adjacent tubes thereby forming an exposed surface spaced from and in thermal comlrnunication With the adjacent tubes, and means for interconnecting said defroster panels on said adjacent tubes so as to vform an integral self-supporting structure with a peripherally extending deicin-g surface spaced from and in thermal communication with said tubes.

References Cited by the Examiner UNITED STATES PATENTS LLOYD L. KING, Primary Examiner. 

1. AN IMPROVED CRYOGENIC VAPORIZER INCLUDING A VAPORIZER TUBE, AN INLET, AND AN OUTLET, SAID TUBE, SAID INLET, AND SAID OUTLET BEING INTERCONNECTED, COMPRISING A PLURALITY OF FINS SECURED TO SAID TUBE IN THERMAL COMMUNICATION THEREWITH, SAID FINS BEING FORMED OF A SINGLE SHEET OF PRESELECTED MATERIAL OF SUBSTANTIALLY UNIFORM THICKNESS AND BEING DISPOSED IN SPACED, PARALLEL RELATIONSHIP TO THE AXIS OF SAID TUBE. 